Discovery of a cyclotron absorption line in the transient X-ray pulsar XTE J1829-098

Understand

We report results of a spectral and timing analysis of the X-ray pulsar XTE J1829-098 using data obtained with the NuSTAR observatory during an outburst in August 2018.

• A strong absorption feature was detected at the energy of $E_{cyc}\simeq 15$ keV in the source spectrum.
• This feature was interpreted as a cyclotron resonance scattering line corresponding to the magnetic field strength of the neutron star surface $B\simeq1.7\times10^{12}$ G.
• The pulse phase-resolved spectroscopy shows that the cyclotron line is significantly detected at all phases of the pulse and its energy and other parameters are variable over the pulse period.